The solenoid is normally on. I think it is part of a panic circuit that
is left over from the heat pump that we don't using any more. So far,
the best we have been able to figure out, the only time it is off is
when the thermostat is turned off. If the furnace is sitting idle it is
still active. From the wiring diagram, very crude and high level, it
shows that its operation is influenced by a flash detector, temperature
sensor (for over heating) and auxiliary input. Haven't determined if
the the aux is hooked up to anything.

What we have observed since I oroginally posted is this:

If the furnace, the circulator is running, the voltage at the solenoid
is about 24 volts but when it shuts down, it goes up to 28 volts. So
something else is putting a load on the same circuit to cause it to
drop.

Our concern is for the solenoid being hot to the touch. Should we be
trying to change the voltage or the amperage to solenoid?

Derek


The solenoid coil is not a resistance, it is an impedance composed of
orthogonal resistive and reactive parts, and this impedance is a strong
function of whether the solenoid is in or out, varying over a 2-3 range.
Placing a resistor in series may very well blow the transformer
because the resistor presents too much drop at "inrush" and the solenoid
hangs at a current loading in excess of the transformer VA.
http://www.radiofrigor.com.br/download/coils.pdf
Your line readings are suspect and unreliable. You don't make it clear
about the solenoid being permanently on or not, , thinking it more
important to tell us totally irrelevant things like it is in a house
belonging to your mother's boyfriend. If this is the kind of thing you
focus on, then stay away from the furnace.